1. Field
Aspects of the present invention generally relate to a sheet conveyance apparatus and an image forming apparatus, and more particularly to the sheet conveyance speed control of conveyance rollers when eliminating a loop formed on a sheet.
2. Description of the Related Art
Conventionally, an image forming apparatuses, such as a copying machine, a facsimile machine, and a printer, has a plurality of conveyance rollers. The image forming apparatus has a sheet conveyance apparatus that uses the plurality of conveyance rollers to convey a sheet to a transfer unit and a fixing unit or, when forming an image on both sides of a sheet, to a two-sided conveyance path. To increase productivity, some sheet conveyance apparatuses have conveyance rollers, which have different sheet conveyance speeds, on the sheet conveyance path depending on the intended use.
However, when the sheet conveyance speed differs between the neighboring conveyance rollers, a loop (mountain-shaped bend) is sometimes formed in a sheet between the conveyance rollers due to a difference of the sheet conveyance speeds or, conversely, a loop is sometimes eliminated when the sheet is pulled. When a loop is eliminated, a sheet sometimes collides with the guide plate of the sheet conveyance path, generating a noise. In addition, when a loop is eliminated with a sheet rubbing against a guide member, the image or the sheet may be damaged.
This phenomenon frequently occurs in a curved sheet conveyance path due to the shape of the sheet conveyance path and the orientation of a sheet. To address this problem, Japanese Patent Application Laid-Open No. 7-315622 discusses the following configuration. That is, to reduce a noise or to reduce rubbing between a sheet and a guide member when a loop is eliminated, the guide member is configured to freely swing when a loop portion of the sheet abuts on the guide member.
However, the above-described conventional sheet conveyance apparatus has a complex configuration for guide-member swing, which makes the apparatus large and expensive. In addition, a recent image forming apparatus is becoming even more productive and a paper-to-paper distance is becoming shorter. This configuration sometimes causes a guide member, which is swung because of a loop in the preceding sheet, to collide with the following sheet when the guide member returns to the original position. In this case, the noise becomes larger.
To realize higher productivity, a recent image forming apparatus tends to control predetermined conveyance rollers to increase the sheet conveyance speed quickly. This conveyance control quickly eliminates a loop formed on a sheet, and causes the sheet to collide with a guide plate with the result that the noise is generated more frequently.